Topic: Thought I had it, dang carb tuning

[eigenvector]

My newly rebuilt bike is still getting the last of it's gremlins out.  One short circuit in the left turn signal, and a carburetor issue that needs to be addressed now.

I can live with the short circuit, but the carb needs to be figured out before I can even really ride this thing.

Starts right up when cold and choked.  Idles smoothly, although one of my valves is too loose because I can hear it tapping.  As soon as I roll on the throttle and release the clutch - <cough ..... flatline>.  If I open the throttle to something like 3 or 4k I can get past it, but anything less and it dies.  Has to be the slow jet/s I'm thinking .  Second issue is when the bike is warm, and it appears to be getting warm quickly - it doesn't want to start.  Acts like it's not getting gas.  As soon as choke is put on - <BAM> starts right up.  Idle remains smooth.  "Acts like it's not getting gas.  As soon as choke is put on - <BAM> starts right up." that is what concerns me the most here.

My 2 cents:  I think it's running way too lean and the slow jets are gummed up.  Obviously the solution is to clean them, but I don't want to chase ghosts here if someone else has another opinion about this.

[hsas.69]

Sounds like your on the right track. I would give the carbs a good thorough cleaning. Definitely sounds like your lean and the idle jets would be most suspect.

[Johnie]

Yah, give the carbs a real good clean. Sometimes you have to use the process of elimination. Plus, while the carbs are apart you will want to check to see where the PO has the needles and floats set. I take it the tank is spotless inside? You talking about the 550?

[Duanob]

Check for a vacuum leak too. New o-rings between the intakes and head? Rubber intake couplers in good shape?

[eigenvector]

Rubber intake couplers are all in good shape.  Harder than rocks, but there is no leak there.

Before I tear down, I want to fiddle with the air cleaner.  I'm currently using one of those plastic and foam rubber replacements and the fit in the air filter box is poor.  Like maybe there's a pretty big air leak there.
Is there a good source for air filters?  I've seriously considered manufacturing one of my own out of sheet aluminum and rivets.

[eigenvector]

So I fiddled with it a bit today.

Despite the rain I re-did the valve gaps, adjusted the #2 exhaust, and refitted a new air cleaner - much snugger fit.

The end result is that it runs just fine now.  A tad uneven in the idle, but tolerable.  At this point I think syncling the carbs will take care of that.  Timing is spot on.

It won't be winning any races, but I was able to accelerate smoothly to backroad speed.  Cruised around 4 1/2 K without any signs of a flat spot.

Ultimately I think the issue that I was having was that the air cleaner was just not fitting properly, leaving a big gap for air the come in.

Incidentally - the throttle return spring is way too heavy.  My original one busted, so I improvised by replacing it with a hardware store spring that fit.  Too heavy though.  Anyone know what the return spring specs are?  I'll need to replace that spring or my arms will break trying to work that throttle.